import java.util.Scanner;

public class Average4 {
 public static void main(String[] args) {
   
   double sum = 0;
   int count = 0;
   while(true) {
     int number = nextInt();
     if(number == 0) {
        break;
     }
     sum += number;
     count++;
   }
   System.out.printf("Æ½¾ù %.2f%n",sum/count);
 }

 static Scanner console = new Scanner(System.in);

 static int nextInt() {
  String input = console.next();
  while(!input.matches("\\d*")) {
    System.out.println("ÇëÊäÈëÊý×Ö");
    input = console.next();
  }
  return Integer.parseInt(input);
 } 

}

